Existing planar radiating element and manifold technology using high dielectric constant materials cannot provide an integrated manifold and radiating element feed layer and good scan and polarization performance. Conventional probe fed patch apertures have gain and polarization limitations. Electronically scanned arrays often employ a circularly polarized field for satellite communication. Single linear polarization imposes inherent limitations on satellite communication. Dual polarization, with signals 90° out of phase, would be preferable if it could be achieved per-unit-cell in the array.
Electronically scanned antennas are fabricated as multilayer printed wiring boards and generally include a feed layer and a manifold layer for distributing power to the feed layer. The feed layer feeds power to an aperture layer that couples the power to free space. The aperture layer typically requires low dielectric constant materials that are unsuitable for standard printed wiring board manufacturing processes. Further, existing aperture layers are substantially thicker than the manifold or feed layers, creating an unbalanced printed circuit board.
Probe fed apertures generally include a low dielectric constant substrate and two printed circuit board patches. Patches tend to scatter into lower order Floquet modes. Lower order Floquet modes must be relatively constant over the scan volume and frequency band, necessitating a small unit cell size and a low dielectric constant substrate. The small unit cell size results in a high module density, significantly increasing the cost of the antenna and increasing the heat dissipation problems. Further, aperture performance as a function of frequency and scan angle is sub-optimal. Cross-polar coupling at wide H-plane scan angles is also high because the probe is asymmetrical with respect to the H-plane.
Probe coupled radiating elements combine the manifold and feed layers of a comparable aperture coupled radiating element resulting in a significant reduction in cost and manufacturing complexity. Current planar radiating element technology cannot provide a relatively broadband (−30%) probe coupled dual polarized radiating element comprised exclusively of epoxy-based printed circuit board materials (e.g., FR-4), manufactured using standard printed circuit board (PCB) processes, and with a built in radome. Conventional probe coupled radiating elements require higher cost polytetrafluoroethylene-based materials that are more expensive and difficult to manufacture than epoxy-based materials (e.g., FR-4). In addition, the unit cell size of a conventional probe coupled radiating element is small. Small unit cell size radiating elements are more expensive, and create module count, packaging, and heat dissipation problems.